2 The golden age of seaplanes is long gone… because of:Higher weightHigher dragCorrosion
3 Power-to-weight ratio of planing boats and airplanes
4 Empty weight to Maximum take-off weight of commercial seaplanes and landplanes
5 Empty weight to Maximum take-off weight of LSA seaplanes and landplanes
6 Advantages of composite structures for amphibious aircraft Eliminate corrosionReduce weightCheaper maintenance and longer lifeImproved shape – lower drag
7 Sandwich structures -lighter, because they are stiffer -cost-effective -can be more damage tolerant -provide flotationSingle Skin Laminate- Blunt Projectile DamageSandwich Laminate- Blunt Projectile DamagePhoto by High Modulus (NZ) Ltd.
8 Application of the progress in planing boats design Optimization of planing hullformsResistanceLongitudinal and lateral stabilityExperience with composite hull structuresDesignUsage
9 Amphibious aircraft design is multidisciplinary by nature – there are contradicting requirements for aerodynamics, structural performance and hydrodynamic properties :PlaningStable Take-off – low drag and spray, longitudinal stability – porpoisingHull loads during take-off and landingDisplacement regimeSeaworthines – hull volumeLateral stability
10 Traditional design of seaplanes Use of semi-empirical equations based on statistical dataData obtained from model scale testsExperience from former projectsSequential determination of design parametersTo explore new designs physics based models should be introduced
11 Challenges for the high-fidelity CAD based analysis methods(Navier-Stokes fluid flow and FEM structural analyses)High complexity of the flowVery high computational costNumerical noise due to discretizationImpossible to explore large design spacesThe solution:Use metamodels (models of models) for MDO
12 Benefits of metamodels: Merging of data from simulation and experimental analysisFiltering of numerical noise and experimental errorsLow computational cost – rapid exploration of the design spacePossible to use gradient-based optimization methodsVisualization of the dependencies
13 Flying boat hull definitions Beam load coefficientDisplacement Froude Number
14 Comparison of the hull resistance of planing boats and hydroplanes
15 Flying boat design is determined by the take-off condition Most important parameter - beam Classic approach – empiricalMunroΔ – weight [kg]b- beam [m]
16 Application of planing boats data: Diehl Determination of beam from thehydrodynamic lift coefficientBeamK=K(β, Clmax)S – wing surface
17 Determination of beam for lateral stability in planing bmin (β, Δ)[m] = 0,5 + 0,0004 Δ[kg]-0,55 β[rad]Longitudinal stability in planingForebody length/beam>3Seaworthiness requirementsHull volume>3*displacement
18 MDO methodologyCreate physics based metamodels for the drag and weight of a seaplane hull as functions of length to beam ratio and deadrise angleDetermine the constraints from the hull volume requirements and the necessary forebody lengthCalculate the design pressures(CS-23)Build a Pareto front and select the design parameters according to mission and seaworthiness requirements.
19 Response surfaces Weight / min weight (L/b, βº) Constant volume of hullCx / Cxmin (L/b, βº)
21 Design Study – Composite amphibious aircraft investigation The benefits from replacing the Al alloy structure with CFRP sandwich one and optimizing the geometry of the planing hull
22 Future WorkImprove the metamodels with application of kriging or radial basis functions
23 References1.Diehl, W. – The application of basic data on planing surfaces to the design of flying-boat hulls, NACA rep No 696, 19402. Munro, W. – Проектирование и расчет гидросамолетов – Москва 1935
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